Surfing a wave to Stockholm

by Clifford M. Will, CQG Editor-in-Chief


What a week for gravitational physics!   

First came the September 27th announcement of another detection of gravitational waves, this time by the three-detector network that included Virgo along with the two LIGO observatories. The source of the gravitational waves was another fairly massive black hole binary merger, with black holes of 30 and 26 solar masses. Once again, about 3 solar masses were converted to energy in a fraction of a second, leaving behind a 53 solar mass black hole spinning at about 70 percent of the maximum allowed. With  Virgo included in the detection, the localization of the source on the sky was improved dramatically over earlier detections by LIGO alone, dropping to a small blob on the sky measuring 60 square degrees, from the large, 1000 square degree banana-shaped regions of earlier detections.

For the first time, a test of gravitational-wave polarizations was carried out.  Because the arms of the two LIGO instruments are roughly parallel, they have very weak sensitivity to different polarization modes of the waves.  But with Virgo’s very different orientation, it was possible to show that the data favor the two spin-2 modes of general relativity over pure spin-0 or pure spin-1 modes.

But then, six days later came the announcement of the Nobel Prize in Physics, awarding one half of the prize to Rainer Weiss of MIT and the other half shared between Kip Thorne and Barry Barish of Caltech, for decisive contributions to the detection of gravitational radiation. CQG congratulates the winners!

Can observations determine the quantum state of the very early Universe?

by Ivan Agullo, Abhay Ashtekar and Brajesh Gupt


Can observations determine the quantum state of the very early Universe?

Can we hope to know even in principle what the universe was like in the beginning? This ancient metaphysical question has acquired new dimensions through recent advances in cosmology on both observational and theoretical fronts. To the past of the surface of last scattering, the universe is optically opaque. Yet, theoretical advances inform us that dynamics of the universe during earlier epochs leaves specific imprints on the cosmic microwave background (CMB). Therefore, we can hope to deduce what the state of the universe was during those epochs. In particular, success of the inflationary scenario suggests that the universe is well described by a spatially flat Friedmann, Lemaître, Robertson, Walker (FLRW) space-time, all the way back to the onset of the slow roll phase. This is an astonishingly early time when space-time curvature was some 10^{65} times that on the horizon of a solar mass black hole and matter density was only 11 orders of magnitude smaller than the Planck scale.

Clockwise from top left: Gupt, Ashketar and Agullo

Clockwise from top left: Brajesh Gupt (Pennsylvania State University), Abhay Ashtekar (Pennsylvania State University) and Ivan Agullo (Louisiana State University)

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Amaldi12 – The Edoardo Amaldi Conference on Gravitational Waves

It’s been a busy few weeks for CQG – we’ve been to the Era of Gravitational Wave Astronomy conference in Paris, hosted the annual Editorial Board meeting in London, attended the Loops17 conference in Warsaw and now it’s time to fly off to California for Amaldi12.

Amaldi12

Amaldi12, named after Edoardo Amaldi, will be held at the Hilton Hotel in Pasadena, CA from 9th – 14th July. The conference will explore the science around gravitational waves and their detection, particularly in light of the confirmed detections by LIGO-Virgo and new advances with the LISA mission.

I will be at the conference Monday through Friday with a table top booth at the event, located near the international ballroom in the hotel. I’m really interested in hearing your thoughts about the journal, so please do stop by say hello and have a chat.

Congratulations to Dr Bernard Kelly, CQG Reviewer of the Year

Classical and Quantum Gravity is proud to recognise excellence in peer review and acknowledge our reviewers for their invaluable contribution to the journal.

Bernard Kelly

Bernard Kelly, University of Maryland, Baltimore County & NASA Goddard Space Flight Center

Congratulations to Dr Bernard Kelly who has won our newly introduced ‘Reviewer of the Year‘ title for his excellent referee reports throughout 2016.  Below Dr Kelly gives us some insight into his process of reviewing and tells us a little bit more about himself.

Tell us how you go about reviewing an article?

First I sit on it for a week or so, thinking “Sounds appropriate. I’ll take a look when I get the chance”. And then the next thing, the journal is pinging me with a follow-up notification, which is when I realise I’ve let too much time slip by.

I read the title, abstract, gloss over the Introduction, and try to assess how mathematically involved the text is, and how much overlap there is with my own areas of expertise (or at least competence). I don’t expect to be familiar with all aspects of the research, but if it’s 50% or better (in whatever fuzzy metric I’m using), I think it’s worth giving it a serious look. Occasionally, I find that what I thought was going to be a good fit wasn’t on closer inspection, and I end up declining.

Now I print the paper out: in colour, if I’m feeling extravagant with my lab’s resources, but usually in B & W. It’s impractical to mark up PDFs on a laptop; perhaps it’d be better on a full-size tablet, but I don’t have one yet. I break out two pens — usually blue & red.

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The Era of Gravitational-Wave Astronomy

At the beginning of next week I will be attending the Era of Gravitational Wave Astronomy conference (or TEGRAW 2017, for short) at the Institut D’Astrophysique in Paris, France.

tegraw

The conference aims to highlight the most recent developments in both theoretical works (such as the two-body problem, effective theories, numerical relativity, and tests of gravity theories) and experimental works (such as future detectors, both on ground and in space).

IOP Publishing/ CQG will have a small table top booth at the event so feel free to stop by if you fancy having a chat. I’ll only be there Monday through Wednesday (unfortunately missing the social event) but am looking forward to meeting you.

I hope to see you in Paris!

A brief history of Supergravity: the first 3 weeks

StanleyDeser2009_01

Stanley Deser is emeritus Ancell Professor of Physics at Brandeis University and a Senior Research Associate at Caltech

Background
Prior to Supergravity’s (SUGRA’s) inception, the ideas in the air came from two new, quite different realms.  One realm was supersymmetry (SUSY); the other arose from the emerging difficulties in achieving consistent interactions between gravity and higher (s > 1) spin gauge fields.

Indeed, the Western discoverers of SUSY, Julius Wess and Bruno Zumino [1], would frequently visit Boston from NYU to spread the SUSY gospel, which did get even our blasé attention after a while, especially since the simplest SUSY multiplet pattern (s; s + 1/2) linking adjoining Fermi-Bose fields had no obvious reason to stop at the s = 0 and s = 1/2 models that had been studied thus far.
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Interview with Daniela Saadeh: winner of the IOP Gravitational Physics Group (GPG) thesis prize

Daniela Saadeh

Daniela Saadeh – UCL Astrophysics Group

CQG is proud to sponsor the IOP Gravitational Physics Group (GPG) thesis prize. This year the prize was awarded to Daniela Saadeh, who we have interviewed below. Congratulations Daniela!

Can you tell us a little bit about the work in your thesis?

A fundamental assumption of the standard model of cosmology is that the large-scale Universe is isotropic – i.e. that its properties are independent of direction. Historically, this concept stemmed from the Copernican Principle, the philosophical statement that we do not occupy a ‘special’ place in the Universe. In physical terms, this idea is converted into the assumption that all positions and directions in the Universe are equivalent, so that no observer is ‘privileged’.

However, assumptions must be tested, especially foundational ones. General relativity – our standard theory of gravity – allows for many ways in which spacetime could be anisotropic: directional symmetry is not fundamentally required. If the Universe were indeed to be anisotropic, we would actually need to carefully revise our understanding (for instance, calculations about its history or content). Making this health check is very important! Continue reading